New data recast whale studies

Monday

Aug 27, 2012 at 2:00 AM

Dave Wiley, research director of the Stellwagen Bank National Marine Sanctuary, and his colleagues hope to use their findings to push for changes in fishing and shipping rules to protect the humpbacks.

KELLY SLIVKA

WOODS HOLE — When the whale known as Touche is hungry for a school of fatty fish, he circles below them, fashioning a net of air by streaming bubbles from his blowhole. Then he corkscrews toward the surface of the Gulf of Maine, herding the fish into an ever tighter packet with the bubbles and his 30-ton body. Finally he opens his jaw wide, takes a monstrous gulp and relaxes, breathing deeply at the water's surface.

Then he dives again. Over and over.

Touche's feeding strategy, captured in June by an electronic tag attached to his back, is of keen interest to scientists tracking North Atlantic humpback whales off Cape Cod.

"Every time we go out and put another tag on, we learn something else," said Dave Wiley, research director of the Stellwagen Bank National Marine Sanctuary.

For Wiley — who returned to shore recently after plying Stellwagen's waters for two weeks with researchers from several institutions — the most striking insight is that each humpback has its own set of behaviors.

"We've got examples sometimes of hundreds of feeding events that are almost all identical for that particular whale but are different than the hundred feeding events that we have for a different whale," he said.

As a result, Wiley's papers about the humpback are full of caveats.

"It's frustrating and complicated and fascinating all at the same time," he said.

Wiley and his colleagues hope to use their findings to push for changes in fishing and shipping rules to protect the humpbacks.

The Stellwagen sanctuary is prime habitat for a pencil-size schooling fish called the sand lance that draws a host of predators, from the humpbacks to fin whales, minke whales, dolphins, striped bass and bluefin tuna.

Yet the sanctuary's proximity to land — 25 miles from Boston and three miles from Province-

town — also means it is heavily used by humans.

On a bright summer day, its waters may be packed with half a dozen whale-watching boats and thousands of recreational and commercial fishing vessels, sailboats and yachts — and that's just at the surface. The depths abound with ropes connecting strings of lobster pots and webs of fixed fishing gear that stretch across like tennis nets.

Most human-caused deaths of humpbacks occur when whales are struck by passing ships or become entangled in fishing gear, Wiley said. But policymakers have not been able to reduce the risks without knowing more about how the whales move underwater.

"Our whole goal is to collect data to influence policy," Wiley said.

For decades, humpback behavior was poorly understood because of the difficulty of shadowing the whales as they roamed the North Atlantic. The breakthrough was the D-tag, engineered in 1999 at the Woods Hole Oceanographic Institution.

Unlike satellite tags, which transmit location, typically over a long period of time, D-tags stay attached for 36 hours at most and record information like speed, depth and audio. They also carry a three-axis accelerometer that measures the front-to-back, side-to-side orientation of the whale.

Heading out for two weeks each summer since 2002, Wiley and a handful of colleagues have successfully tagged humpbacks 90 times, in some cases the same individuals over multiple years. The tag data are overlaid with acoustical studies of prey biomass and, for the past two summers, images from National Geographic's so-called Crittercams, which bring back video showing how whales use different parts of their bodies while feeding and coordinate their movements while traveling in groups.

The data have revolutionized humpback research and conservation in the sanctuary, showing scientists where the whales spend their time in the water column while on a dive, what they do at different depths, how they move around and when they vocalize.

"The D-tag is sort of a revelation and a revolution," said Ari Friedlaender, a marine ecologist at Duke University who has taken part in the Stellwagen project since 2006.

The tag, about the size of a pack of Twinkies, has four suction cups and is attached to a whale by extending a pole.

The tag is programmed to pop off after a predetermined time, although some get bumped off or shaken off early. Then it floats to the surface, where the researchers retrieve it and download its data.

Scientists have been focusing on New England's humpback whales since the late 1970s, when they realized that each one had a unique pattern of pigmentation on the underside of its tail, said Peter Stevick, an ecologist at the College of the Atlantic in Bar Harbor, Maine, which maintains the official North Atlantic Humpback Whale Catalog, a compilation of photographs of whales' tails taken all over the North Atlantic. Today it contains photographs of about 7,000 individuals, taken by scientists, whale enthusiasts and tourists. (Stevick estimates the global humpback population at around 20,000.)

He said multiple sightings of individuals help researchers understand the whales' travels. For example, humpbacks photographed feeding in the Gulf of Maine in the summer have been photographed in the winter in the Caribbean, where they mate and calve.

Slowly but steadily, there have been payoffs from this research.

In 2007 the shipping lanes between Boston and New York, which cross the Stellwagen sanctuary, were shifted to avoid whale-packed areas, partly because Wiley's D-tag data showed that humpbacks spent 60 percent of their time within 50 feet of the surface, in striking distance of boats' hulls.

In 2009 the National Oceanic and Atmospheric Administration began requiring fisheries to use ropes that sink rather than traditional floating ones to connect lobster pots and crab traps. The floating ropes arch above the sea floor, posing a potential risk to deep-diving whales, but no one realized that until the Stellwagen D-tag data showed whales diving straight to the bottom and rooting around.

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